In refining chemical and petrochemical applications, conventional scallops are used in radial flow reactors and function as conduits through which gases, vapors or liquids (hereinafter referred to collectively as “G-V-L” or “feedstock”) flow inside the reactor vessel. Scallops are typically formed as elongated, tube-shaped conduits of various geometry, typically having a cross-sectional “D” shape (although other shapes are also used), through which G-V-L flow radially in an inward or outward direction relative to the vessel. The scallops are typically formed of various metal constructions, sometimes having openings on a surface thereof to allow the G-V-L to flow freely through the surface of the scallop, as well as along the length of the scallop. When the G-V-L flows through the scallop and escape through the openings on the surface, it comes into contact with catalyst particles contained within an adjacent catalyst bed (annulus space), thus causing a reaction to take place. In use, the scallops are placed adjacent to one another along the inner circumference of the wall of the reactor vessel. Scallops in the art have generally used holes of uniform size and distribution over the body of the scallop.
In refining chemical and petrochemical applications in radial flow reactors, conventional outer baskets may also be used in place of, or in addition to, the scallops discussed above. These outer baskets provide the same function as the scallops, i.e., as conduits through which G-V-L flow inside the reactor vessel. Outer baskets are typically formed as one continuous basket, such as a cylindrical-shaped conduit of various geometry, through which G-V-L flow radially in an inward or outward direction relative to the vessel. The outer basket is typically formed of various metal constructions, sometimes having openings on a surface thereof to allow the G-V-L to flow freely through the surface of the outer basket, as well as along the length of the outer basket. When the G-V-L flows through the outer basket and escapes through the openings on the surface, it comes into contact with catalyst particles contained within an adjacent catalyst bed (annulus space), thus causing a reaction to take place. In use, the outer basket is placed along the inner circumference of the wall of the reactor vessel. Outer baskets in the art have generally used profile wire with various wire slot openings of uniform size and distribution over the body of the outer basket.
Likewise, conventional center pipes are also used in radial flow reactors and function as conduits through which G-V-L flow inside the reactor vessel. Center pipes are typically formed as one continuous cylinder, through which G-V-L flow radially in an inward or outward direction relative to the vessel. The center pipe is typically formed of various metal constructions, sometimes having openings on a surface thereof to allow the G-V-L to flow freely through the surface of the center pipe, as well as along the length of the center pipe. When the G-V-L flows through the adjacent catalyst bed, the center pipe acts as the collection/outlet device after the reaction has taken place. In use, the center pipes are placed directly in the center of the reactor to create a uniform annulus for the catalyst bed of the reactor vessel. Center pipes in the art generally have holes of uniform size and distribution over the surface of the center pipe to hydraulically control the adjacent catalyst bed. The center pipe is then generally wrapped with a wire mesh or profile wire material for the purpose of catalyst containment.
One common problem with such designs is that as the G-V-L enters the scallop or outer basket, a higher volume of the G-V-L outflows through the openings of the scallop or outer basket where the pressure drop of the system is lower. This difference in flow could be seen in both the axial and radial directions. This uneven flow distribution through and along the scallop or outer basket, results in an uneven utilization of the catalyst in the catalyst bed. Specifically, the top part of the catalyst bed is prone to be utilized more quickly, while the bottom part of the catalyst bed is slow to be utilized. This can cause a number of problems, most significantly (and costly) that the uneven flow distribution reduces the resulting reaction efficiency of the vessel.
Accordingly, systems and methods of improving the flow distribution of G-V-L through the reactor vessel are needed, in order to increase reaction efficiency, catalyst activity, and catalyst bed uniformity, so as to extend the lifespan of the catalyst, and to increase reactor equipment efficiencies and ancillary equipment performance. More specifically, a system that causes a more uniform pressure drop and therefore G-V-L flow in the reactor system is desired.